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    <title>Graph2d | Interpolation</title>
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<h2>Graph2d | Interpolation</h2>
<div style="width:700px; font-size:14px; text-align: justify;">
    The Graph2d makes use of <a href="http://en.wikipedia.org/wiki/Centripetal_Catmull%E2%80%93Rom_spline" target="_blank">Catmull-Rom spline interpolation</a>.
    The user can configure these per group, or globally. In this example we show all 4 possiblities. The differences are in the parametrization of
    the curves. The options are <code>uniform</code>, <code>chordal</code> and <code>centripetal</code>. Alternatively you can disable the Catmull-Rom interpolation and
    a linear interpolation will be used. The <code>centripetal</code> parametrization produces the best result (no self intersection, yet follows the line closely) and is therefore the default setting.
    <br /><br />
    For both the <code>centripetal</code> and <code>chordal</code> parametrization, the distances between the points have to be calculated and this makes these methods computationally intensive
    if there are very many points. The <code>uniform</code> parametrization still has to do transformations, though it does not have to calculate the distance between point. Finally, the
    linear interpolation is the fastest method. For more on the Catmull-Rom method, <a href="http://www.cemyuksel.com/research/catmullrom_param/catmullrom.pdf" target="_blank">C. Yuksel et al. have an interesting paper titled &Prime;On the parametrization of Catmull-Rom Curves&Prime;</a>.
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<div id="visualization"></div>

<script type="text/javascript">
    // create a dataSet with groups
    var names = ['centripetal', 'chordal', 'uniform', 'disabled'];
    var groups = new vis.DataSet();
    groups.add({
        id: 0,
        content: names[0],
        options: {
            drawPoints: false,
            interpolation: {
                parametrization: 'centripetal'
            }
        }});

    groups.add({
        id: 1,
        content: names[1],
        options: {
            drawPoints: false,
            interpolation: {
                parametrization: 'chordal'
            }
        }});

    groups.add({
        id: 2,
        content: names[2],
        options: {
            drawPoints: false,
            interpolation: {
                parametrization: 'uniform'
            }
        }
    });

    groups.add({
        id: 3,
        content: names[3],
        options: {
            drawPoints: { style: 'circle' },
            interpolation: false
        }});

    var container = document.getElementById('visualization');
    var dataset = new vis.DataSet();
    for (var i = 0; i < names.length; i++) {
        dataset.add( [
            {x: '2014-06-12', y: 0 , group: i},
            {x: '2014-06-13', y: 40, group: i},
            {x: '2014-06-14', y: 10, group: i},
            {x: '2014-06-15', y: 15, group: i},
            {x: '2014-06-15', y: 30, group: i},
            {x: '2014-06-17', y: 10, group: i},
            {x: '2014-06-18', y: 15, group: i},
            {x: '2014-06-19', y: 52, group: i},
            {x: '2014-06-20', y: 10, group: i},
            {x: '2014-06-21', y: 20, group: i}
        ]);
    }

    var options = {
        drawPoints: false,
        dataAxis: {visible: false},
        legend: true,
        start: '2014-06-11',
        end: '2014-06-22'
    };
    var graph2d = new vis.Graph2d(container, dataset, groups, options);

</script>
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